This invention relates to a steerable axle assembly of the type including steering knuckles pivotally mounted on king pins provided at opposite ends of an axle beam and more particularly to mechanism for insuring proper lubrication thereof.
A steerable axle assembly of the type disclosed herein includes at each end a steering knuckle having upper and lower sections straddling an axle beam and provided with cylindrical bores which receive end pivot portions of a king pin mounted on the axle assembly.Such axle assemblies are known as "reverse Elliott" axle assemblies. Bushings are generally disposed between the king pin pivot portions and the upper and lower knuckle sections. If dirt, water, or other foreign matter is permitted to work into a position between the king pin pivot portions and the bushings in the upper and lower knuckle sections, erosion of these parts is greatly accelerated. Accordingly, it is important that mechanism be provided for sealing the cooperating bearing portions of the steering knuckle and king pin to prevent the ingress of dirt and moisture which contaminates the lubricant and abrades the moving parts.
One type of sealing and lubricating structure comprises end spindle lubricating mechanism including flat cover plates for covering the open ends of the bores in the steering knuckles. "Grease zirks" or lubricant fittings, which comprise check valves, are mounted on the plates for introducing lubricant to the ends of the king pin receiving bores for passage between the king pin and bushings. In the end spindle greasing system, the operator is assured that lubrication process is complete when he observes lubricant passing between the inside of the bifurcated yoke portions and the axle beam. End spindle greasing sometimes causes turbulence in the grease which builds the internal pressure to such a level that it damages or "pops" the bearing seals.
Another type of steerable axle assembly includes a knuckle incorporating side spindle lubrication fittings at the side of the knuckle assembly for introducing lubricant to the pivot pin receiving bores therein. In the side spindle greasing system, lubricant is admitted to the side of the bores intermediate opposite ends thereof for passage in axially opposite directions toward the opposite ends of the bifurcated yoke portions. If the outer bore end remains uncovered, dirt, water, and other foreign matter may enter and corrode and erode the parts. If closure plates are used to completely close the outside ends of the knuckle bores, the operator has no assurance that the outer king pin ends are completely lubricated. It is not unusual for the lubricator to erroneously interrupt the lubrication process as soon as he has observed lubricant passing between the inside of the yoke portions and the axle beam. When lubrication is so interrupted, the outer ends of the king pivot pin portion and the bushings may not be fully lubricated in which case wear of the pivot pins and bushings remote from the beam would quickly erode, necessitating an early replacement of the parts. Apparatus constructed according to the present invention includes an end plate provided with a check valve which permits lubricant to pass only outwardly from the outer ends of the king pin receiving bores. With such a system, the operator, upon seeing the lubricant pass through the check valves, can be certain that lubricant has passed completely to the outer ends of the king pin and yet the king pin is protected from dirt entering via the outer ends of the bore.
In the system disclosed herein, an end plate is aligned with each knuckle bore and an annular seal is provided between each end plate and the knuckle to prevent the escape of lubricant therebetween. The plate could be substantially flat but then the knuckle must include a recessed portion adjacent the bore to receive a portion of the annular shaft seal so that lateral movement of the seal perpendicular to the axis of the bore is prohibited. Such machining of the knuckle is expensive. Accordingly, it is an object of the present invention to provide an end cap having an annular recess for receiving a portion of an annular seal which bears against the steering knuckle.
As the bushings and pivot pin portions heat while in use, it is desirable to automatically provide an increased supply of lubricant to the bearing surfaces. The apparatus constructed according to the present invention incorporates an end cap having a lubricant reseervior which receives and stores lubricant when the bearing parts are not heated for supply to the bearing parts as they are used and become hot. Accordingly, it is an object of the present invention to provide a steerable axle assembly of the type described having an end closure plate of the type described provided with a central lubricant reservoir surrounded by an annular recess for receiving an annular sealing element.
It is another object of the present invention to provide a steerable axle assembly of the type described including an end cap having a lubricant reservoir disposed in alignment with the king pin receiving bore and having a check valve lubricant fitting communicating therewith for passing lubricant axially outwardly.
It is a further object of the present invention to provide a steering axle assembly of the type described including a snap type, expansible and retractible disc type plug closing one end of the knuckle bore and being wedged into the wall of the bore to close the bore and including a lubricant emitting check valve which passes lubricant only axially out of the bore.
It is yet another object of the present invention to provide a steering axle assembly of the type described includng a side spindle lubricant introducing system which will include mechanism for providing a positive indication as to when lubrication has been completed.
It is another object of the present invention to provide a steering axle assembly of the type described which will increase the reliability of proper lubrication by unskilled mechanics.
It is yet another object of the present invention to provide a steering axle knuckle assembly of the type described including a lubricant introducing fitting in the side thereof and having an end plate with an annular recess receiving a sealing ring at the junction of the knuckle and the spiral bushing.
These and other objects of the present invention will become apparent to those of ordinary skill in the art as the description thereof proceeds.